import java.util.Scanner;

public class Area {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请选择s.t.c");
        char a = input.next().charAt(0);
        int area;
        double are;

        switch(a)
        {
            case 's':
            case 'S':
                int c = input.nextInt();
                area= c*c;
                System.out.printf("%d",area);
                break;
            case 't':
            case 'T':
                int d = input.nextInt();
                area = d*d/2;
                System.out.printf("%d",area);
                break;
            case 'c':
            case 'C':
                int e = input.nextInt();
                are = 3.14*e*e;
                System.out.printf("%f",are);
                break;
        }


    }
}
